It’s true the Lutron sensors are very quick. And it’s true that the Lutron/smartthings integration may slow things down a bit as it’s cloud to cloud. so It all depends on exactly what you need.
In my case, I’m using HomeKit for this, not smartthings, so everything runs locally. No cloud latency. And I’m in a wheelchair, so a slight delay may not be as much of an issue for me as someone walking.
Personally, I use both hue motion sensors and Aqara zigbee motion sensors, but I don’t know what would be the quickest when used with smartthings. Hopefully others will chime in.
Historically, Zigbee sensors have tended to be a bit quicker than zwave sensors for some technical reasons, but the newer generation of zwave, the ones with the 700 series chip, are faster than earlier generations.
The first thing, regardless of the protocol you are using, is to understand how PIR (passive IR) sensors work. Many people think they are a cameralike device, and set them up so that they are pointing towards the object to be detected. But that actually will give you the slowest response. Because these devices measure very slight changes in heat passing across the field of detection, you will typically get the best results when they are placed 90° to the object to be detected. There is a community FAQ about this:
FAQ: Where to locate motion sensor for fastest response?
Sometimes the best thing to do is to put them on the ceiling pointing downwards just outside a room and then you can catch someone as they approach a room rather than waiting until they are through the doorway. That in itself can give you an extra second or so. Anyway, just something to think about. 